The present invention relates generally to the art of electric motors and other electromechanical machines. More particularly, the invention relates to an improved winding arrangement for the stator of an electromechanical machine.
Electric motors and other electromechanical machines are generally constructed having a cylindrical stator core. The inner circumference of the stator core defines a plurality of radial slots in which electrical windings are maintained. As is well known, current flow through the windings produces a rotating magnetic field which the rotor of the machine will tend to follow.
The stator windings of an AC induction motor are typically arranged into a plurality of coil groups, with each coil group providing a single pole of a single phase. Each side of an individual coil typically shares a particular winding slot with one side of another coil in a different coil group. Thus, a common three-phase, two-pole induction motor will have a total of six coil groups. Typically, each of the coil groups in such a motor will be configured having eight coils, yielding a total of forty-eight coils. These forty-eight coils have a total of ninety-six coil sides, located in forty-eight winding slots.
The art has developed several winding patterns in which the coil groups can be arranged. For example, one arrangement that has seen widespread use in industry is the xe2x80x9clap winding.xe2x80x9d In this arrangement, one side of a coil will be in the xe2x80x9cbottomxe2x80x9d of a particular winding slot, while the other side of the same coil will be positioned in the xe2x80x9ctopxe2x80x9d of another slot several slot positions away. Moreover, the respective sides of every coil will be separated by the same number of slot positions. Thus, the individual coils overlap each other around the inner circumference of the stator core.
Another common winding arrangement is referred to as a xe2x80x9cconcentric winding.xe2x80x9d In this type of arrangement, coils within a group are organized concentrically, such that sides of each coil will be separated by a different number of slot positions.
xe2x80x9cLap windingsxe2x80x9d and xe2x80x9cconcentric windingsxe2x80x9d each offer certain advantages not offered by the other. For example, lap windings typically exhibit outstanding operational characteristics. The lap winding process, however, has been extremely difficult to automate. Concentric windings, on the other hand, are amenable to automation. Thus, concentric windings are often preferred when motor cost is a significant factor.
While cost considerations tend to make the use of concentric windings desirable, it has not been possible to provide concentric windings in all motor sizes. For example, it has been found necessary to manually wind motors of 200 HP or larger with a lap winding pattern. This is due to the nature of a concentric winding pattern, in which the motor""s lead wires must be attached to only one side of the stator core. With the large lead wires required at higher power levels, a standard frame size, such as a NEMA 440 frame, simply does not provide sufficient clearance to route the lead wires to the frame""s conduit box opening. A lap winding pattern permits smaller lead wires to be connected at each end of the stator core, which are more easily routed to the conduit box opening in the frame.
The present invention recognizes and addresses the foregoing disadvantages, and others, of prior art constructions and methods. Accordingly, it is an object of the present invention to provide a novel winding arrangement for the stator of an electromechanical machine.
It is a more particular object of the present invention to provide a novel winding arrangement of the concentric winding type.
It is a specific object of the present invention to provide a concentric winding arrangement that permits connection of motor leads to windings at both ends of the stator core.
It is a specific object of the present invention to provide a novel winding arrangement that facilitates automated winding of stators intended for use in large electric motors.
Some of these objects are achieved by a stator assembly for an electromechanical machine comprising a magnetically permeable stator core. The core has a cylindrical inner surface defining a plurality of radial, axially-extending winding slots. At least six coil groups of electrical windings are also provided, each of the coil groups having a plurality of winding coils arranged concentrically. A predetermined number of winding coils within each group are singularly located in spaced apart pairs of winding slots. In addition, the remaining number of winding coils within each coil group is shared in spaced-apart pairs of winding slots along with coil sides of winding coils in other groups.
For example, each coil group may comprise a total of six winding coils. In such embodiments, two of the six winding coils may be singularly located in winding slots and the remaining four may share winding slots with other coil sides. Often, the magnetically permeable core may define a total of forty-eight winding slots.
Preferably, the stator core may comprise a number of power leads equal to the number of coil groups. The power leads are preferably arranged such that an equal number will be connected to the electrical windings at each end of the stator core. For example, if the stator assembly has a total of six power leads, three of the power leads may be connected to electrical windings at each of the stator core""s two ends.
Other objects of the present invention are achieved by a stator assembly for an electromechanical machine comprising a magnetically permeable stator core. The core has a cylindrical inner surface defining a plurality of radial, axially-extending winding slots. At least six coil groups of electrical windings are also provided, each of which has a plurality of winding coils arranged concentrically. The stator assembly includes a number of power leads equal to a number of coil groups. The power leads are connected to electrical windings at each end of the stator core.
The stator assembly may be configured having a total of six coil groups arranged to provide a three-phase, two-pole stator assembly. In such embodiments, three power leads are preferably connected to electrical windings at each end of the stator core.
It will often be advantageous to include a total of six winding coils within each of the coil groups Two of the six winding coils are singularly located in winding slots and four of the six winding coils share winding slots with coils of other groups.
Still further objects of the present invention are achieved by a method of producing a stator assembly for use in an electromechanical machine. One step of the method involves providing a magnetically permeable stator core having a cylindrical inner surface defining a plurality of radial, axially-extending winding slots. At least six coil groups are also provided, each having a plurality of differently-sized winding coils. The coil groups are inserted into the stator core one at a time from alternating sides thereof.
According to exemplary methodology, each of the coil groups are inserted such that a predetermined number of winding coils are singularly located in spaced apart pairs of winding slots. A remaining number of winding coils may be placed in spaced apart pairs of winding slots along with coil sides of winding coils in other groups. Preferably, the coil groups may be inserted in the stator core such that winding coils that are singularly located in one coil group are positioned adjacent to winding coils that are singularly located in another coil group within a mutual phase.
Other objects, features and aspects of the present invention are provided by various combinations and subcombinations of the disclosed elements, as well as methods of practicing same, which are discussed in greater detail below.